1. Field of the Invention
The invention relates to a thread device for a sewing machine including a thread spool wound with thread to be fed to a stitching section of a sewing machine.
2. Description of the Related Art
Conventionally, an automatic thread feeding device for a home-use sewing machine feeds a necessary amount of thread for forming one stitch in sewing operation. This kind of automatic thread feeding device is disclosed, for example, in U.S. Pat. No. 5,010,834.
On the other hand, in sewing operations, such as forming embroidery patterns, and stitching together fabrics having different colors or patterns, it is required to exchange thread during the sewing.
When exchanging thread in a conventional home-use sewing machine, thread spools have been generally exchanged by hand. In an industrial embroidery sewing machine, various color-thread spools are set in advance and the spools are automatically exchanged in sequence to form multi-color patterns.
However, the exchange of thread spools by hand as in the home-use sewing machine makes the operation troublesome and reduces work efficiency as the number of colors increases. On the other hand, for example, U.S. Pat. No. 5,881,660 discloses the automatic exchange of thread for the industrial sewing machine. This kind of automatic exchange is superior in work efficiency, but it needs a complicated exchanging device in much higher cost, which makes it difficult to apply the device to a relatively low price home-use sewing machine.
It is therefore an object of the invention to provide a sewing machine that is able to exchange thread efficiently with relatively simple structure in lower cost.
In order to solve the problems mentioned above, the invention provides a thread device for a sewing machine as exemplified in FIGS. 11 and 12 as a first aspect of the invention.
The thread device includes:
a spool mounting member (spool bars 31 and 32) which rotatably supports a thread spool wound with thread to be fed to a needle of the sewing machine and is attached to a machine body of the sewing machine;
a thread winding mechanism (thread winder unit 30) which is connected to the thread spool and feeds the thread backward, being fed from the thread spool to a needle side, to the thread spool;
a feed mechanism (feed roller 11 and feed motor 12) which is disposed on a thread path between the thread winding mechanism and the needle of the sewing machine and performs an operation feeding the thread of the thread spool to the needle side and an operation feeding the thread in the needle side to a side of the thread winding mechanism;
a thread detecting mechanism (upper thread state detecting sensor 20) which is disposed between the feed mechanism and the thread winding mechanism and generates a first detecting signal when detecting the thread in a tense state;
a feed-backward amount detecting mechanism (wound-amount measuring counter) which generates a second detecting signal when an amount of the thread fed backward to the thread spool by the thread winding mechanism reaches a given value; and
a controller (CPU 81a) which feeds a given amount of the thread to the side of the thread winding mechanism by operating the feed mechanism when the first detecting signal is generated by the thread detecting mechanism, repeats a feed-backward operation in which the given amount of the thread is fed backward by the thread winding mechanism after feeding the given amount of the thread, and stops winding when the second detecting signal is generated by the feed-backward amount detecting mechanism.
According to the first aspect of the invention, the thread is automatically wound under the control of the controller, so that the winding process is made easier, resulting in improved efficiency of exchanging spools. In addition, the feed means is used for winding the thread as well as supplying the thread in a sewing process, utilizing a conventionally mounted structure, and therefore the winding mechanism is realized in relatively lower cost.
For the winding method by the winding mechanism, each spool is rotated via the spool mounting member, or instead the thread may be wound around a fixed spool. The winding mechanism may be fixedly installed on the machine, or may be prepared as an independent device.
Further, the method of detecting the winding of a given amount of thread is properly selectable. For instance, the winding operation can be stopped as the completion of the winding after a certain time has elapsed without detecting the tense state of thread by the detecting means, because, when the tense state of thread is not detected by the detecting means while the winding mechanism continues to wind the thread, this means that the thread end has passed out the feed means.
As another way, the length of thread fed out from the spool is known, for example, as the length from the spool mounting member to a sewing needle through a predetermined route. Therefore, storing a winding amount of thread in a memory based on this length, and counting the wound amount of thread, the winding can be stopped when the counted value reaches the stored value.
In a second aspect of the invention, the controller obtains a reference wound amount from an amount wound by the thread winding mechanism and uses the reference wound amount as a reference value for a wound amount in a following process.
According to the second aspect of the invention, when a thread length to be wound is given, a multiplying number of the reference wound amount for completing the winding can be obtained. That is, quantitative control can be easily performed as in obtaining the driven number of the feed means.
In a third aspect of the invention, the thread winding mechanism includes:
a motor which rotates the thread spool in a feed-backward direction; and
a transmitting mechanism which transmits drive of the motor to the thread spool.
According to the third aspect of the invention, when the thread winding device is attached to the machine, the device automatically winds the thread, to thereby effectively wind the thread and make the exchange of spool easier.
In a fourth aspect of the invention, the motor is attached to the machine body of the sewing machine, and
the transmitting mechanism is attached to the spool mounting member and includes:
a coupling member which is couplable and uncouplable with respect to a drive shaft of the motor; and
a coupling mechanism which couples the coupling member to the thread spool.
Accordingly, the spool mounting member is attachable to the machine body of the sewing machine and the spool mounting member can be miniaturized and made lighter.
In a fifth aspect of the invention, a thread device for a sewing machine, includes:
spool mounting members each of which rotatably supports a thread spool wound with thread different from the other thread to be fed to a needle of the sewing machine and is attached to a machine body of the sewing machine;
a motor which rotates the thread spool in a feed-backward direction; and
a transmitting mechanism which transmits drive of the motor to the thread spool; and
a switching mechanism (switching arm holding member 60) which selectively couples one of the thread spools to the transmitting mechanism.
According to the fifth aspect of the invention, a plurality of thread spools are provided and thread of one of the thread spools can be selectively wound by the switching mechanism. Accordingly, during sewing with the use of thread from one spool, another spool can be mounted on the other spool mounting members, so that, after finishing the sewing, the thread from the latter spool can be used for sewing upon winding up the thread of the former spool by the winding device. This operation is especially useful in such a case that the thread needs to be frequently exchanged as in embroidery sewing.
The switching means can employ an electrical driving source such as a motor or a solenoid, or a mechanically linked switching mechanism to be manually operated.
In a sixth aspect of the invention, the thread device according to the fifth aspect is characterized in that,
the switching mechanism includes:
a switching drive source which electrically operates and is attached to the machine body of the sewing machine; and
a lever which is attached to the spool mounting member and couples the transmitting mechanism to one of the thread spools by an operation of the switching drive source.
According to the sixth aspect of the invention, the device can be miniaturized and made lighter because the drive source for winding operation is equipped inside the machine body.